Three-Dimensional (“3D”) printing is an additive manufacturing process in which successive layers of material are laid down on top of each other to form a solid 3D object. Over time, various types of 3D printing process have been developed, including extrusion-based 3D printing (e.g., fused deposition modeling (FDM)), and processes based on light polymerization, such as stereolithography (SLA) and digital light processing (DLP), among others.
In stereolithography processes, a 3D structure is built up one layer at a time, with each layer being formed by exposing a photo-reactive resin to an ultraviolet (UV) light source that cures the resin. Note that stereolithography may also be referred to as optical fabrication, photo-solidification, and/or solid free-form fabrication and solid imaging.
More specifically, in a typical stereolithography process, a digital 3D model of an object is created by a user via the software interface of a 3D printing application. The 3D printing application then slices the 3D model with a set of horizontal planes. Each slice of the 3D model can then be converted to a two-dimensional mask image, such that the 3D model is represented as a sequence of two-dimensional mask images, each of which outline the shape of the corresponding layer from the 3D model. The mask images are sequentially projected onto a photo-curable resin surface so as to cure the resin in the shape of the layer. Alternatively, instead of using masks, each slice of the 3D model may be representing by a two-dimensional image in the shape of the slice, so that a projector can project a sequence of such two-dimensional images onto the resin surface to form an object corresponding to the digital 3D model.